In recent years, there is a rapid increase in a rate and a capacity of packet data traffic in a mobile communication cellular system, particularly in downlink. This makes it necessary to develop a wireless transmission method for realizing high efficiency and large capacity. A method of providing high speed transmission using adaptive modulation or using multilevel modulation preferentially for a terminal user near a base station and present in good propagation environment has been developed and worked (see, for example, Non-patent Document 1).
There is also conventionally known a method of preventing crosstalk in a CDMA (Code Division Multiple Access) system by transmitting same signals using the same code from two base stations using soft handover at the time of a handover from a cell 1 to a cell 2 (see, for example, Patent Document 1).
Moreover, there is proposed an MBMS method for improving characteristics by similarly transmitting the same data from two base stations corresponding to two cells, respectively, and selectively receiving the data (see, for example, Non-Patent Document 2).
Furthermore, there is proposed a MIMO method for realizing high efficiency propagation in multipath environment by transmitting different information to respective transmitting antennas between a transmitter including a plurality of antennas and a receiver including a plurality of antennas (see, for example, Patent Document 2).
There is further proposed transmission diversity in a cellular wireless communication system (see, for example, Patent Document 3). A system proposed performs transmission diversity by allocating different orthogonal codes to a first base station and a second base station, respectively.    [Patent Document 1]
Japanese Patent Application Laid-Open (JP-A) No. 6-169485    [Patent Document 2]
JP-A-2005-176376    [Patent Document 3]
JP-A-2004-64240    [Non-Patent Document 1]
Umesh, Moon, Ishii, and Nakamura, “Selective Combining for W-CDMA Multimedia Broadcast Multicast Service (MBMS)”, IEICE Conference, B-5-148, 2004 March    [Non-Patent Document 1]
3GPP, “Physical Layer Aspects of UTRA High Speed Downlink Packet Access”, Chapter 6.2 (page 12), TR25-848